WO1999052130A1 - Exposure method, exposure apparatus, method of producing the same, device, and method of fabricating the same - Google Patents

Abstract

A main controller (50) determines an exposure control desired value according to the transmittance of an optical system (28A, 28B, 32, PL) measured by means of a sensor (59) before the exposure or estimated by predetermined calculation and controls the exposure according to the determined exposure control desired value while a reticle pattern is being transferred onto a wafer (W) through the optical system. Since the exposure energy given to the image surface in a unit time over unit area changes with the transmittance of the optical system, the exposure control desired value is determined according to the transmittance of the optical system, and the exposure is controlled according to the determined control desired value. Therefore, high-precision exposure is achieved without being influenced by the variation of the transmittance.

Description

 Specification

EXPOSURE METHOD, EXPOSURE APPARATUS AND ITS MANUFACTURING METHOD, AND DEVICE AND ITS MANUFACTURING METHOD

 The present invention relates to an exposure method, an exposure apparatus and a method for manufacturing the same, and a device and a method for manufacturing the same. More specifically, the present invention relates to an exposure apparatus used in photolithography when manufacturing semiconductor elements, liquid crystal display elements, and the like. And an exposure method performed by the exposure apparatus, a device manufacturing method using the exposure method, and a device manufactured by the exposure apparatus. Background art

 Conventionally, in the photolithography process for manufacturing semiconductor devices or liquid crystal display devices, a step-and-repeat type reduction projection exposure apparatus (a so-called stepper) and a step-and- Projection exposure apparatuses such as scanning type scanning exposure apparatuses (so-called scanning and stepper) are mainly used.

 The resolving power of the projection optical system constituting this type of projection exposure apparatus is expressed by the relationship of R = kXA / NA, as is well known by Rayleigh's equation. Here, R is the resolution of the projection optical system, λ is the wavelength of the exposure light, 光. Ν is the numerical aperture of the projection optical system, and k is a constant determined by the process in addition to the resolution of the resist.

As semiconductor devices become more highly integrated, the resolution required for projection optical systems becomes increasingly finer.To achieve this, as can be seen from the above equation, the wavelength of the exposure light can be shortened and the aperture of the projection optical system can be reduced. Efforts are being made to increase the number, a so-called high N. In recent years, a krypton fluoride excimer laser (KrF excimer laser) having an output wavelength of 248 nm has been used as a light source for exposure, and the numerical aperture of the projection optical system has also been increased to 0. Six or more exposure systems have been put to practical use, and exposure with a device rule (practical minimum line width) of 0.25 AI m has been realized.

 In the above-described conventional projection exposure apparatus, under the assumption that the transmittance of the optical system does not change due to the irradiation of the exposure light, the exposure amount control is performed as follows. That is, the amount of exposure light irradiated on the reticle in front of the projection optical system is measured in advance by a light amount monitor (called an integrator sensor) arranged in the illumination optical system, and the light amount on the rear side of the projection optical system is measured. The light intensity of the exposure light transmitted through the reticle and the projection optical system is measured by a light intensity monitor on the wafer stage, for example, an illuminometer, and the output ratio between the integrator sensor and the illuminometer is determined in advance. At the time of exposure, the illuminance of the wafer surface (image surface) is estimated from the output value of the integrator sensor using the output ratio, and the exposure amount is feedback-controlled so that the illuminance of the image surface becomes a desired value. . Recently, as a light source following the krypton fluoride excimer laser, an argon fluoride excimer laser (ArF excimer laser) having an output wavelength of 193 nm has attracted attention. If an exposure apparatus using this argon fluoride excimer laser as an exposure light source is put into practical use, mass production of microdevices having a fine pattern ranging from 0.18 m to 0.13 im device rule will be possible. And vigorous R & D is being actively pursued.

 However, in the case of an exposure apparatus that uses an ArF excimer laser as the light source for exposure, the fact that the transmittance of the optical system (illumination optical system and projection optical system) changes at a non-negligible level due to exposure light exposure. There was found. Recent studies have shown that the transmittance of an optical system is characterized by the fact that it gradually increases after the start of exposure light and reaches a saturation level when it increases to a certain level.

That is, it is considered that such a change is due to a cleaning effect, in which moisture and organic substances attached to the surface of an optical element such as a lens or a reflecting mirror are removed from the surface of the optical system by irradiation with an ArF excimer laser beam. . Although this cleaning effect is thought to have occurred in the case of the KrF excimer laser light, the ArF excimer laser In the case of the KrF excimer laser light, there is a large difference in transmittance between the case where water droplets are present and the case where water droplets are not present. Probably not.

 The conventional exposure amount control method described above, which assumes that the transmittance of the optical system does not change due to exposure light irradiation, cannot be adopted as it is.

 The present invention has been made under such circumstances, and a first object of the present invention is to provide an exposure method capable of realizing high-precision exposure without being affected by fluctuation in transmittance of an optical system. It is in.

 A second object of the present invention is to provide an exposure apparatus capable of realizing high-precision exposure without being affected by fluctuations in transmittance of an optical system. Disclosure of the invention

 According to a first aspect, the present invention provides an optical system (28A, 28B, 3B) for transferring a pattern illuminated by exposure light (EL) from a light source (16) onto a substrate (W). 2. An exposure method performed by an exposure apparatus including: PL), wherein a first step of setting an exposure control target value according to the transmittance of the optical system; and Transferring the pattern onto the substrate via the optical system while controlling the amount of exposure based on the second step.

Here, the exposure amount control target value is not a target integrated exposure amount to be given on an image plane (substrate surface) determined according to the sensitivity of the resist on the substrate, but the target integration exposure amount. In the present specification, the term "exposure amount control target value" is used in this specification. According to this, in the first step, the exposure control target value is set according to the transmittance of the optical system, and in the second step, the exposure is controlled while controlling the exposure based on the set exposure control target value. The pattern is transferred onto the substrate via the optical system. That is, the exposure energy given to the image surface per unit time per unit area according to the transmittance of the optical system is Therefore, if the exposure amount control target value is set according to the transmittance of the optical system and exposure is performed at the set exposure amount, as in the present invention, a highly accurate Exposure can be achieved.

 As a countermeasure against transmittance fluctuations, the time change of transmittance is measured in advance under the same illumination conditions as during exposure, and the transmittance time change curve is obtained.At the time of exposure, the elapsed time from the start of irradiation and the stop of irradiation The time is measured by a timer, the transmittance is estimated by calculation using the time data and the transmittance time change curve, and the result of this calculation is compared with the output of the light amount monitor arranged in the illumination optical system. A method is conceivable in which the image plane illuminance is estimated based on the illuminance and the amount of exposure is controlled so that the image plane illuminance becomes a desired value. In addition to the need for complicated pre-measurement operations, the value estimated by calculation does not always match the actual transmittance.

 In the exposure method according to the present invention, the transmittance of the optical system, which is a reference for setting the exposure value control target value in the first step, can be actually measured at a predetermined measurement interval. In such a case, the transmittance measurement is performed at a predetermined measurement interval. Until the next transmittance measurement, the exposure control target value is set according to the transmittance measured before, and the exposure light amount is controlled based on the set exposure control target value. The pattern illuminated with the exposure light from the light source is transferred onto the substrate via the optical system. Therefore, in addition to eliminating the need for the above-described complicated preliminary measurement operation, the exposure control target value is set based on the actually measured transmittance, and the exposure control target value is set based on the set exposure control target value. As a result, the illuminance (image surface illuminance) on the substrate surface can always be set to a desired (appropriate) value, and high-precision exposure can be performed.

The variation of the transmittance of the optical system varies depending on the exposure conditions. Considering this, in the exposure method according to the present invention, it is preferable that the measurement interval is set according to exposure conditions. In such a case, depending on the exposure conditions, A transmittance measurement interval is set, and transmittance measurement is performed at the set measurement interval. Until the next transmittance measurement, the exposure control target value is set according to the transmittance measured before, and the exposure is controlled based on the set exposure control target value. Then, the pattern illuminated by the exposure light from the light source is transferred onto the substrate via the optical system. Therefore, according to the present invention, irradiance (image surface illuminance) on the substrate surface can be always set to a desired (appropriate) value regardless of the exposure conditions, and high-precision exposure can be performed. Also in this case, the complicated preliminary measurement operation described above is not required.

 The exposure condition is a condition that is a reference for setting a measurement interval of the transmittance of the optical system. The exposure condition includes everything that affects the transmittance of the optical system. For example, the exposure condition may include the transmittance of a mask (R), or the exposure condition may include any of a minimum line width and an exposure tolerance.

 In the exposure method according to the present invention, when the transmittance of the optical system, which is a reference for setting the exposure amount control target value, is actually measured at a predetermined measurement interval, the measurement interval is obtained by the transmittance measurement immediately before. The change may be made according to the amount of change between the obtained transmittance and the transmittance obtained by the transmittance measurement before that. In such a case, the transmission interval between subsequent transmissions is changed according to the amount of change between the transmittance obtained by the previous transmittance measurement and the transmittance obtained by the previous transmittance measurement. Therefore, it is necessary to measure the transmittance frequently.Thus, the throughput measurement interval is shortened in the period where the transmittance change rate is large, and in the opposite case, the throughput measurement interval is lengthened, so that the throughput is unnecessary. It is possible to realize high-precision exposure amount control without any reduction.

The inventors of the present application have performed analysis based on transmittance change curves obtained by various experiments, and as a result, have found that an exposure apparatus using an ArF excimer laser beam (or an illumination light having a shorter wavelength) as a light source. It has been found that there is a predetermined relationship between the temporal change of the transmittance of the optical system during exposure and the irradiation history of the exposure light since the previous stop of the apparatus. Therefore, in the exposure method according to the present invention, the first step includes the step of irradiating the optical system (28A, 28B, 32, PL) with exposure light (EL) according to the irradiation history of the optical system. The method may include: a prediction function determining step of determining a transmittance time change prediction function; and a step of setting the exposure control target value based on the determined transmittance time change prediction function.

 According to the present invention, a time change prediction function of the transmittance of the optical system in accordance with the irradiation history of the exposure light to the optical system is determined, and the exposure amount control target value is determined based on the determined time change prediction function of the transmittance. When the pattern is transferred, the exposure is controlled based on this exposure control target value, so that it is predicted based on the time change prediction function of the transmittance without frequent transmittance measurement during exposure. It is possible to accurately control the amount of exposure (predictive control) according to the transmitted light, and consequently keep the image plane illuminance (substrate plane illuminance) almost at the desired value without unnecessarily lowering the throughput. Can be set.

 In the above-mentioned prediction function determination step, the irradiation history of the exposure light to the optical system is considered as described above, as described above, as a result of the research by the inventors, the rate of change of the transmittance of the optical system (change rate) It has been found that it depends on the irradiation history of the exposure light with respect to. Therefore, the time change prediction function according to the present invention means an expression including a parameter depending on the irradiation history of the exposure light to the optical system.

The time change function is, for example, T is an optical system transmittance, a is a parameter representing the change rate, and bi is a parameter depending on each exposure condition including an illumination condition.

Can be used.

In the exposure method according to the present invention, prior to the predictive function determining step, the time during which the apparatus was previously stopped during operation, and the time when the optical system was irradiated with exposure light during self-cleaning thereafter And measuring the exposure light intensity and the integrated irradiation amount.

 In this specification, “self-cleaning” means a break-in operation performed after the start of operation of the apparatus. This is because the surface (optical thin film surface) of each lens element that composes the optical system is contaminated with contaminants (organic substances and moisture) during the stoppage of the operation of the optical system. This is because the irradiation of the exposure light has an effect (cleaning effect) that the contaminants are gradually peeled off from the surface of each lens element. The reason why the cleaning is not simply called is that the cleaning effect naturally occurs even during the exposure, and is distinguished therefrom.

The irradiation history is determined according to each of the above physical quantities from the last stop of the apparatus to the start of actual exposure of the substrate, so that the time during the last stop of the apparatus operation and the subsequent exposure light exposure to the optical system during self-cleaning are performed. By actually measuring the irradiation time, the exposure light intensity, and the integrated irradiation amount to obtain the irradiation history, an accurate exposure amount prediction function can be determined. In the exposure method according to the present invention, it is more desirable that the environmental conditions of the optical system are measured at predetermined time intervals, and these factors are taken into account when determining the function of predicting the change in transmittance with time. Studies of the inventors, the temperature and humidity in the chamber where the exposure apparatus main body is housed, an optical system, for example, environmental conditions such as atmospheric pressure or C 0 ₂ concentration in the lens chamber in the projection optical system, transmittance of the optical system This has been found to have an effect on the rate of change. The exposure method according to the present invention may further include a step of measuring the transmittance of the optical system at predetermined intervals, and may correct the transmittance time change prediction function each time the transmittance is measured. Since it is difficult to predict the change in transmittance of the optical system completely accurately, it is better to measure the change in transmittance at a predetermined interval and correct the error in the predicted value of the exposure amount generated during the predetermined interval. This is because it is possible to control the exposure amount more accurately in the layer.

In this case, it is preferable that the measurement interval of the transmittance is determined according to the relationship with the required exposure accuracy. In such a case, when the required exposure accuracy is severe, the measurement interval should be shortened and the transmittance time change prediction function should be set to a finer interval. By reducing the error in the calculated predicted value of transmittance by correcting the exposure, if the required exposure accuracy is gradual, increase the measurement interval to prevent unnecessary decrease in throughput. Becomes possible.

 Also, since the rate of change of the transmittance (rate of change) is not uniform, for example, the transmittance measurement interval should be shortened during the period when the rate of change of the transmittance of the optical system is large, and longer when the rate of change is opposite. You may do it. In such a case, it is possible to prevent the throughput from being inadvertently reduced while maintaining the exposure amount control accuracy.

 According to a second aspect of the present invention, a pattern illuminated with exposure light (EL) from a light source (16) is formed on a substrate using an optical system (28A, 28B, 32, PL). (W) an exposure apparatus for transferring onto the substrate, an exposure setting apparatus for setting an exposure control target value according to the transmittance of the optical system; and transferring the pattern onto the substrate via the optical system. An exposure amount control system (50) for controlling an exposure amount based on the set exposure amount control target value.

 According to this, an exposure amount setting device sets an exposure amount control target value in accordance with the transmittance of the optical system, and the exposure amount control system transfers the pattern onto the substrate via the optical system during the transfer (ie, exposure). Medium), the exposure is controlled based on the set exposure control target value. As described above, since the exposure energy applied to the image plane per unit time per unit area changes according to the transmittance of the optical system, the exposure amount control target value is set according to the transmittance of the optical system as in the present invention. By setting and controlling the exposure amount based on the set exposure amount control target value, the illuminance of the substrate surface (image surface illuminance) is always a desired (appropriate) value without being affected by the transmittance fluctuation. , And exposure can be performed with high accuracy.

When the exposure apparatus according to the present invention further includes a transmittance measurement device (46, 59, 50) for measuring the transmittance of the optical system, the exposure amount setting device includes the transmittance measurement device. The exposure value control target value can be set according to the transmittance measured by the apparatus. In such a case, the transmittance of the optical system is measured by the transmittance measuring device. The exposure ratio is measured, and the exposure setting device sets an exposure control target value according to the measured transmittance. When transferring the pattern, the exposure amount is controlled by the exposure amount control system based on the set exposure amount control target value. This eliminates the need for complicated pre-measurement operations as in the case of obtaining the transmittance time change curve described above, and in addition to the exposure control target value set based on the actually measured transmittance. Since the amount of exposure is controlled, the illuminance (image surface illuminance) on the substrate surface can always be set to a desired (appropriate) value, and high-precision exposure can be performed.

 In this case, the transmittance measurement device (46, 59, 50) may perform the transmittance measurement at a predetermined measurement interval. In such a case, the transmittance measurement is performed at predetermined intervals by the transmittance measuring device. Until the next transmittance measurement, an exposure control target value is set by the exposure setting device according to the transmittance measured before, and the exposure control system sets the target during exposure. The exposure amount is controlled based on the exposure amount control target value. Therefore, in addition to eliminating the need for the complicated pre-measurement operation described above, the exposure control target value is set based on the actually measured transmittance, and the exposure control is performed based on the set exposure control target value. The exposure amount is controlled, and each time a new transmittance is measured, the exposure target value is updated and set according to the transmittance at that time, and the exposure is controlled based on the updated exposure control target value. Is done. Accordingly, the illuminance (image surface illuminance) on the substrate surface can always be set to a desired (more appropriate) value, and high-precision exposure can be performed in a state in which the influence of the transmittance fluctuation is further reduced.

The variation of the transmittance of the optical system varies depending on the exposure conditions. In consideration of this, it is preferable that the exposure apparatus according to the present invention further includes a control device that sets the measurement interval of the transmittance measurement device according to exposure conditions. In such a case, the control device sets the measurement interval of the transmittance of the optical system in accordance with the exposure condition, and the transmittance measurement device executes the transmittance measurement at the set measurement interval. Until the next transmittance measurement, the transmittance previously measured by the exposure setting device is used. An exposure control target value is set in accordance with the excess rate, and during the transfer of the pattern to the substrate via the optical system, the exposure control system controls the exposure based on the set exposure control target value. If the exposure condition is changed during the execution of the exposure processing operation, the control unit updates and sets the measurement interval of the transmittance measurement device according to the changed exposure condition. Subsequent transmittance measurements will be performed. Therefore, if the exposure condition is an exposure condition in which a large change in transmittance is likely to occur, the transmittance measurement interval should be shortened, and if the exposure condition has a gentle change in the transmittance, the transmittance measurement interval should be increased. Can be. Therefore, high-precision exposure can be realized without changing the exposure conditions, without being affected by the fluctuation of the transmittance, and without unnecessarily reducing the throughput. Also in this case, the complicated preliminary measurement operation described above becomes unnecessary.

 The exposure apparatus according to the present invention, further comprising: an information reading device that reads information on a mask on which the pattern is formed, when the control device sets a measurement interval of the transmittance measurement device according to exposure conditions. In this case, the control device may automatically set the measurement interval of the transmittance measurement device based on the read information of the mask.

 In the exposure apparatus according to the present invention, the measurement interval of the transmittance in the transmittance measurement device is set according to the amount of change between the transmittance measured immediately before by the transmittance measurement device and the transmittance measured before the transmittance measurement device. The control device may be further provided. In such a case, the control device sets the measurement interval of the transmittance in the transmittance measurement device according to the amount of change between the transmittance measured by the transmittance measurement device and the transmittance previously measured. Therefore, it is necessary to measure the transmittance frequently.The transmittance measurement interval is shortened in the period where the transmittance change rate is large, and in the opposite case, the transmittance measurement interval is lengthened, thereby making the throughput unnecessary. It is possible to realize high-precision exposure without lowering.

In this case, two consecutive measurements of transmittance by the transmittance measurement device are: The measurement may be performed prior to the start of the exposure, or two consecutive measurements of the transmittance by the transmittance measuring device may be performed after the start of the exposure. In the former case, the transmittance measurement interval can be automatically set according to the transmittance of the optical system at the beginning of the exposure.In the latter case, after the exposure starts, the transmittance In the period where the rate of change is large, the transmittance measurement interval can be automatically set so as to shorten the transmittance measurement interval, and vice versa.

 In the exposure apparatus according to the present invention, when the exposure apparatus further includes a first optical sensor (46) for detecting a light amount of the exposure light (EL) applied to the pattern, the exposure control system (50) Preferably, during the transfer of the pattern to the substrate, the exposure is controlled based on the exposure control target value and the output of the first optical sensor. In such a case, the actual exposure amount is obtained based on the light amount detected by the first optical sensor, and the exposure amount is filtered so that the difference (deviation) between the exposure amount and the exposure amount control target value becomes zero. High-precision exposure amount control becomes possible by performing one-back control.

In the exposure apparatus according to the present invention, the transmittance measuring apparatus is, for example, substantially the same as the second optical sensor (46) for detecting the amount of the exposure light (EL) applied to the pattern, and the substrate. A second optical sensor (59) provided on a surface, and detecting a light amount of the exposure light passing through the optical system at a timing according to an exposure condition using the second optical sensor; A control device for determining the transmittance of the optical system based on the amount of light and the output of the first optical sensor (46) may be included. In such a case, at a predetermined timing according to the exposure condition, the controller uses the second optical sensor provided on substantially the same surface as the substrate to measure the amount of the exposure light passing through the optical system. Then, the transmittance of the optical system is determined based on the detected light amount and the output of the first optical sensor. The exposure setting device sets (updates) the exposure control target value in accordance with the measured (determined) transmittance, and performs the exposure control based on the updated exposure control target value. The exposure amount during pattern transfer is controlled by the system. This allows high accuracy without being affected by fluctuations in optical system transmittance. Exposure can be realized.

 Also in this case, it is preferable that the exposure control system controls the exposure based on the exposure control target value and the output of the first optical sensor during the transfer of the pattern to the substrate. .

 In this case, the timing for executing the light amount detection of the exposure light passing through the optical system for updating the exposure amount control target value may be determined according to the exposure condition that affects the transmittance of the optical system. For example, the control device may detect the amount of the exposure light that has passed through the optical system at a timing according to the transmittance of the mask (R) on which the pattern is formed. The apparatus may detect the light amount of the exposure light that has passed through the optical system at a timing in which one of the minimum line width and the exposure amount allowable error is considered.

 When the exposure apparatus according to the present invention further includes an arithmetic unit (50) that determines a time-change prediction function of the transmittance of the optical system according to the irradiation history of the exposure light to the optical system, The exposure setting device may set the exposure control target value based on the transmittance time change prediction function determined by the arithmetic device. According to this, the arithmetic unit determines the transmittance time change prediction function of the optical system in accordance with the irradiation history of the optical system, and based on the determined transmittance time change prediction function, sets the exposure amount setting device. The exposure value is set based on the exposure value control target value, and the exposure value is controlled by the exposure value control system based on the set exposure value control target value during pattern transfer, so that the transmittance is frequently measured during exposure. Without this, accurate exposure amount control (prediction control) according to the transmittance predicted based on the transmittance time change prediction function is possible, and the image plane illuminance (substrate plane illuminance) is almost always the desired value. Once set, the pattern can be transferred onto the substrate using an optical system. Therefore, high-precision exposure can be realized without being affected by a change in the transmittance of the optical system.

In this case, a transmittance measuring device that measures the transmittance of the optical system at predetermined intervals; and a correcting device that corrects the transmittance time change prediction function each time the transmittance is measured. And a device. In such a case, when the transmittance of the optical system is measured by the transmittance measurement device, the correction device can correct the transmittance time change prediction function every time the measurement is performed. The error of the predicted value is corrected at the predetermined interval, so that more accurate exposure amount control becomes possible.

 In this case, a control device that sets a transmittance measurement interval in the transmittance measurement device according to a variation amount between the transmittance measured immediately before by the transmittance measurement device and the transmittance measured before the transmittance measurement device is provided. Further provisions may be made. In such a case, it is necessary to frequently measure the transmittance. In a period in which the rate of change in transmittance is large, the transmittance measurement interval is shortened, and in the opposite case, the transmittance measurement interval is lengthened, thereby increasing the throughput. High-precision exposure can be realized without unnecessary reduction. In the exposure apparatus according to the present invention, the optical system includes: an illumination optical system (12) for illuminating the mask (R) on which the pattern is formed with the exposure light (EL); A projection optical system (PL) for projecting the exposure light onto the substrate (W); a mask stage (RST) for holding the mask; and a substrate stage (58) for holding the substrate (W). Further provisions may be made. According to this, the mask held on the mask stage is illuminated by the exposure light from the illumination optical system, and the pattern of the mask is transferred to the substrate on the substrate stage via the projection optical system. In this case, as described above, the exposure amount control target value is set according to the transmittance of the optical system, and during the transfer of the pattern, the exposure amount is controlled based on the set exposure amount control target value. Therefore, a static exposure type such as a stepper that can always set the illuminance (image surface illuminance) on the substrate surface to a desired (appropriate) value and perform high-precision exposure without being affected by transmittance fluctuations. Is provided.

In this case, the apparatus further comprises a driving device for synchronously moving the mask stage (RST) and the substrate stage (58) in a one-dimensional direction within a plane orthogonal to the optical axis of the projection optical system (PL). be able to. In such a case, the illuminance (image plane illuminance) on the substrate surface is always set to a desired (appropriate) value without being affected by the transmittance fluctuation. And a scanning projection exposure apparatus capable of performing high-precision exposure by setting the scanning projection exposure apparatus.

 According to a third aspect of the present invention, there is provided a method of manufacturing an exposure apparatus for transferring a pattern of a mask onto a substrate, the method comprising: providing an illumination optical system for irradiating the mask with exposure light; Providing a projection optical system for projecting the emitted exposure light onto the substrate; providing a substrate stage for holding the substrate; and an exposure amount control target according to the transmittance of the projection optical system. A method for manufacturing an exposure apparatus, comprising: providing an exposure setting apparatus for setting a value; and providing an exposure control system for controlling an exposure based on the set exposure control target value.

 According to this, the illumination optical system, the projection optical system, the substrate stage, the exposure amount setting device, the exposure amount control system, and various other components are adjusted by mechanically, optically, and electrically combining and adjusting. The exposure apparatus of the present invention can be manufactured. In this case, a static exposure type projection exposure apparatus such as a step-and-repeat method can be manufactured.

 In the method for manufacturing an exposure apparatus according to the present invention, a step of providing a mask stage for holding the mask; and a step of moving the mask stage and the substrate stage one-dimensionally in a plane orthogonal to an optical axis of the projection optical system. Providing a drive that moves synchronously in the direction. In such a case, it is possible to manufacture a scanning type exposure apparatus such as a step-and-scan method capable of controlling the exposure amount by changing and adjusting the relative scanning speed between the mask stage and the substrate stage.

Further, in the lithographic process, by performing exposure using the exposure method of the present invention, a pattern of a plurality of layers can be formed on a substrate with a high degree of superposition accuracy. Can be manufactured with high yield, and the productivity can be improved. Similarly, in the lithographic process, by performing exposure using the exposure apparatus of the present invention, the line width control accuracy is improved by improving the exposure amount control accuracy, whereby a pattern of a plurality of layers is formed on a substrate. Pile It can be formed with high alignment accuracy. Therefore, a highly integrated microdevice can be manufactured with a high yield, and the productivity can be improved. Therefore, from another viewpoint, the present invention is a device manufacturing method using the exposure method of the present invention or the exposure apparatus of the present invention, and can also be said to be a device manufactured by the manufacturing method. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a view schematically showing a configuration of an exposure apparatus according to the first embodiment of the present invention.

 FIG. 2 is a diagram showing an internal configuration of the light source in FIG.

 FIG. 3 is a flowchart showing a control algorithm of the CPU in the main controller of FIG. 1 when a reticle pattern is transferred onto a predetermined number of wafers.

 FIG. 4 is a flowchart showing a control algorithm of a CPU in a main control device when transferring a reticle pattern onto a predetermined number of wafers in the exposure apparatus according to the second embodiment of the present invention. .

 FIG. 5 is a diagram schematically showing a configuration of an exposure apparatus according to the third embodiment of the present invention.

 FIG. 6 shows that after the operation of the exposure apparatus of the third embodiment is stopped, the operation of the apparatus is started, the reticle pattern is transferred onto a predetermined number (M) of wafers W, and the operation of the apparatus is stopped again. 6 is a flowchart showing a sequence up to the point where the operation is performed. FIG. 7 is a flowchart showing a subroutine of step 3222 in FIG. FIG. 8 is a flowchart for explaining an embodiment of the device manufacturing method according to the present invention.

FIG. 9 is a flowchart showing the processing in step 404 of FIG. BEST MODE FOR CARRYING OUT THE INVENTION << 1st Embodiment >>

 Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

 FIG. 1 shows a schematic configuration of an exposure apparatus 10 according to the first embodiment. The exposure apparatus 10 is a step-and-scan type scanning exposure apparatus using an ArF excimer laser light source (oscillation wavelength 1933 η m) as an exposure light source. The scanning exposure apparatus 10 includes an illumination system including a light source 16 and an illumination optical system 12, a reticle stage RST holding a reticle R as a mask illuminated by exposure light EL from the illumination system, and a reticle R. The projection optical system PL that projects the exposure light EL emitted from the substrate onto the wafer W as a substrate, the XY stage 14 equipped with a Z tilt stage 58 as a substrate stage that holds the wafer W, and These control systems are provided.

In practice, the light source 16 is provided with a chamber 11 in which the components of the illumination optical system 12 and the exposure apparatus body including the reticle stage RST, the projection optical system PL, and the XY stage 14 are housed. It is located in a low-clean service room separate from the clean room, and is connected to the chamber 11 via a beam matching unit (not shown). Incidentally, K r F Ekishimare laser light source (oscillation wavelength 2 4 8 nm) as the light source, or F ₂ excimer laser light source may be used (oscillation wavelength 1 5 7 nm) other pulsed light source.

 FIG. 2 shows the inside of the light source 16 together with the main controller 50. The light source 16 has a laser resonator 16a, a beam splitter 16b, an energy monitor 16c, an energy controller 16d, a high-voltage power supply 16e, and the like.

The laser beam LB emitted in a pulse form from the laser resonator 16a is incident on the beam splitter 16b having a high transmittance and a small reflectance, and is transmitted through the beam splitter 16b. Is injected outside. The laser beam LB reflected by the beam splitter 16b is incident on an energy monitor 16c composed of a photoelectric conversion element, and a photoelectric conversion signal from the energy monitor 16c is not shown. Is supplied to the energy controller 16 d as an output ES through the peak hold circuit of FIG.

 At the time of normal light emission, the energy controller 16d sets the output ES of the energy monitor 16c to a value corresponding to the target value of energy per pulse in the control information TS supplied from the main controller 50. The power supply voltage of the high-voltage power supply 16 e is feedback-controlled so that Further, the energy controller 16d changes the oscillation frequency by controlling the energy supplied to the laser resonator 16a via the high-voltage power supply 16e. That is, the energy controller 16 d sets the oscillation frequency of the light source 16 to the frequency instructed by the main controller 50 in accordance with the control information TS from the main controller 50, and Feedback control of the power supply voltage of the high-voltage power supply 16 e is performed so that the energy per pulse becomes the value specified by the main controller 50. Such details are disclosed in detail, for example, in Japanese Patent Application Laid-Open No. 8-250402 and the corresponding US Pat. No. 5,728,495. To the extent permitted by the national laws of the designated or designated elected country in this international application, the disclosures in the above-mentioned gazettes and U.S. patents are incorporated herein by reference.

 Outside the beam splitter 16 b in the light source 16, a shirt 16 f for shielding the laser beam LB in accordance with control information from the main controller 50 is also provided.

 Returning to FIG. 1, the illumination optical system 12 includes a beam shaping optical system 18, a rough energy adjuster 20, a fly-eye lens 22, an illumination system aperture stop plate 24, a beam splitter 26, and a first beam splitter. It has a relay lens 28 A, a second relay lens 28 B, a fixed reticle blind 30 A, a movable reticle blind 30 B, a mirror M for bending the optical path, a condenser lens 32, and the like. In addition, instead of the fly-eye lens 22, an optical lens may be used as an optical lens.

The beam shaping optical system 18 passes through a light transmission window 13 provided in the chamber 11. And is connected to a beam matching unit (not shown). The beam shaping optical system 18 converts the cross-sectional shape of the laser beam LB, which is pulsed by the light source 16 and enters through the light transmission window 13, into a fly-eye lens 2 provided behind the optical path of the laser beam LB. The beam is shaped so that it is efficiently incident on 2, and is composed of, for example, a cylinder lens / beam expander (both not shown).

 The energy rough adjuster 20 is disposed on the optical path of the laser beam LB behind the beam shaping optical system 18, and here, a plurality of different light transmittances (= 1—dimming rates) around the rotating plate 34 are provided. (For example, six ND filters 36A and 36D are shown in FIG. 1), and the rotating plate 34 is driven. By rotating at, the transmittance for the incident laser beam LB can be switched from 100% in geometric progression in multiple steps. The drive motor 38 is controlled by a main controller 50 described later. It is to be noted that a rotary plate similar to the rotary plate 34 may be arranged in two stages so that the transmittance can be more finely adjusted by combining two sets of ND filters.

 The fly-eye lens 22 is arranged on the optical path of the laser beam LB emitted from the energy rough adjuster 20 and forms a number of secondary light sources for illuminating the reticle R with a uniform illuminance distribution. The laser beam emitted from this secondary light source is hereinafter referred to as “exposure light EL”.

An illumination system aperture stop plate 24 made of a disc-shaped member is arranged near the exit surface of the fly-eye lens 22. The illumination system aperture stop plate 24 includes, for example, an aperture stop made of regular circular apertures at equal angular intervals, an aperture stop made of small circular apertures for reducing the coherence factor and value, and an annular stop for annular illumination. A ring-shaped aperture stop and a modified aperture stop with multiple apertures eccentrically arranged for the modified light source method (only two of these apertures are shown in Fig. 1) Has been done. The illumination system aperture stop plate 24 is configured to be rotated by a driving device 40 such as a motor controlled by a main controller 50 described later. One of the aperture stops is selectively set on the optical path of the exposure light EL.

 A beam splitter 26 having a small reflectance and a large transmittance is arranged on the optical path of the exposure light EL emitted from the illumination system aperture stop plate 24, and further, on the optical path behind this, a fixed reticle blind 3OA and a movable reticle are provided. A relay optical system including a first relay lens 28A and a second relay lens 28B is provided with a blind 30B interposed therebetween.

 The fixed reticle blind 30A is disposed on a plane slightly defocused from a conjugate plane with respect to the pattern plane of the reticle R, and has a rectangular opening defining an illumination area 42R on the reticle R. A movable reticle blind 30B having an opening whose position and width in the scanning direction is variable is arranged near the fixed reticle blind 30A, and the movable reticle blind 30B is provided at the start and end of scanning exposure. By further restricting the illumination area 42R via B, unnecessary portions of the exposure are prevented.

 On the optical path of the exposure light EL behind the second relay lens 28B constituting the relay optical system, a bending mirror M for reflecting the exposure light EL passing through the second relay lens 28B toward the reticle R is provided. The condenser lens 32 is arranged on the optical path of the exposure light EL behind the mirror M.

 Furthermore, on one of the optical paths that are vertically bent by the beam splitter 26 in the illumination system 12 and on the other optical path, an integer sensor 46 as a first optical sensor composed of a photoelectric conversion element, reflected light Monitors 47 are arranged respectively. These integrators 46 and reflected light monitor 47 are, for example, PIN type photo diodes that are sensitive in the deep ultraviolet region and have a high response frequency to detect the pulse emission of the light source 16. Etc. can be used.

The operation of the illumination system 12 configured as described above will be briefly described. The laser beam LB pulsed from the light source 16 enters the beam shaping optical system 18 and is then moved to the rear fly-eye lens. 22 The cross-sectional shape is set so that After being shaped, it enters the energy coarse adjuster 20. Then, the laser beam LB that has passed through any of the ND filters of the energy rough adjuster 20 enters the fly eye lens 22. Thereby, a large number of secondary light sources are formed at the exit end of the fly-eye lens 22. The exposure light EL emitted from the many secondary light sources passes through one of the aperture stops on the illumination system aperture stop plate 24 and then reaches a beam splitter 26 having a large transmittance and a small reflectance. The exposure light EL transmitted through the beam splitter 26 passes through the rectangular opening of the fixed reticle blind 30 A and the movable reticle blind 30 B through the first relay lens 28 A, and then passes through the second relay lens. After passing through the lens 28B, the optical path is bent vertically downward by the mirror M, and then passes through the condenser lens 32 to make the rectangular illumination area 42R on the reticle R held on the reticle stage RST uniform. Illumination with a suitable illuminance distribution.

 On the other hand, the exposure light EL reflected by the beam splitter 26 is received by the integrator sensor 46 via the condenser lens 44, and the photoelectric conversion signal of the integrator sensor 46 becomes a peak (not shown). It is supplied to the main controller 50 as an output DS (digit / pulse) via a hold circuit and an A_D converter. The correlation coefficient between the output DS of the integrator sensor 46 and the illuminance (exposure amount) of the exposure light EL on the surface of the wafer W is determined in advance, and the memory 51 provided in the main controller 50 is provided. Is stored within.

 The illuminated area 42 R on the reticle R illuminates and the reflected light flux reflected on the pattern surface of the reticle (the lower surface in Fig. 1) passes through the condenser lens 32 and the relay optical system in the opposite direction to the front. The light is reflected by the beam splitter 26 and received by the reflected light monitor 47 via the condenser lens 48. The photoelectric conversion signal from the reflected light monitor 47 is supplied to the main controller 50 via a peak hold circuit (not shown) and an A / D converter. In the present embodiment, the reflected light monitor 47 is mainly used for pre-measurement of the transmittance of the reticle R. This will be described later.

A reticle R is placed on the reticle stage RST, and a vacuum (not shown) It is sucked and held via a memory chuck. The reticle stage RST can be finely driven in a horizontal plane (XY plane), and can be driven in a predetermined direction in the scanning direction (here, the Y direction, which is the horizontal direction in FIG. 1) by a reticle stage driving unit 48. The scanning is performed in the roak range. The position of the reticle stage RST during this scanning is measured by an external laser interferometer 54 R via a moving mirror 52 R fixed on the reticle stage RST, and the measured value of the laser interferometer 54 R is used. Is supplied to the main controller 50.

The material used for the reticle R needs to be properly used depending on the light source used. That is, when a light source K r F light source and A r F light source, can be have use synthetic quartz, the case of using F ₂ light sources, it is necessary to form fluorite. The projection optical system PL is composed of a plurality of lens elements having a common optical axis AX in the Z-axis direction arranged in a telecentric optical arrangement on both sides. Further, as the projection optical system PL, one having a projection magnification (eg, 8) of, for example, 1/4 or 15 is used. For this reason, as described above, when the illumination area 42R on the reticle R is illuminated by the exposure light EL, the pattern formed on the reticle R is projected by the projection optical system PL. The image reduced in step 13 is projected and transferred to a slit-shaped exposure area 42 W on a wafer W having a resist (photosensitive agent) applied on the surface.

In the case of using the K r F excimer laser light, or A r F excimer laser light as the exposure light EL is as each of the lens elements constituting the projection optical system PL can be used synthetic quartz, F ₂ When excimer laser light is used, fluorite is used as the material of the lens used in the projection optical system PL. The XY stage 14 is two-dimensionally driven by a wafer stage drive unit 56 in a scanning direction 丫 and an X direction perpendicular to the scanning direction (a direction perpendicular to the plane of FIG. 1). The wafer W is held on a Z tilt stage 58 mounted on the XY stage 14 by vacuum suction or the like via a wafer holder (not shown). Is held. The Z tilt stage 58 has a function of adjusting the position (force position) of the wafer W in the Z direction and adjusting the inclination angle of the wafer W with respect to the XY plane.

 That is, although the position of the wafer W in the Z direction is not shown, for example, Japanese Unexamined Patent Publication No. Hei 6-284304 and US Patent No. 5,448,333 corresponding thereto. The output of this focus sensor is supplied to a main controller 50, and a Z tilt stage 5 is provided in the main controller. 8 to perform the so-called focus leveling control. To the extent permitted by the national laws of the designated country or selected elected countries specified in this international application, the disclosures in the above-mentioned publications and US patents are incorporated herein by reference.

 The position of the XY stage 14 is measured by an external laser interferometer 54 W via a moving mirror 52 W fixed on a Z tilt stage 58, and the laser interferometer 54 W Is supplied to the main controller 50.

On the Z tilt stage 58, an irradiation amount monitor 59 as a second optical sensor for detecting the light amount of the exposure light EL passing through the projection optical system PL has a light receiving surface substantially corresponding to the wafer W. It is installed at the same height as the surface. Instead of the irradiation amount monitor, another sensor such as an illuminometer, an irradiation molecular sensor including a pinhole sensor, a photochromic, or an aerial image measuring device may be provided as the second optical sensor. The control system is mainly configured by a main control device 50 as a control device in FIG. The main controller 50 includes a so-called microcomputer (or workstation) including a CPU (central processing unit), a ROM (read / only memory), a RAM (random access memory), and the like. For example, synchronous operation of the reticle R and the wafer W, stepping of the wafer W, exposure timing, and the like are collectively controlled so that the operation is properly performed. In the present embodiment, the main controller 50 also controls the exposure amount at the time of scanning exposure as described later. Specifically, for example, during scanning exposure, the main controller 50 is synchronized with the reticle R being scanned via the reticle stage RST in the + Y direction (or -Y direction) at a speed V r = V. Then, the wafer W is moved through the XY stage 14 in the negative direction (or + Y direction) with respect to the exposure region 42 in the negative direction (or + Y direction) V w =) 8 · V (3 is a projection from the reticle R to the wafer W. Reticle stage RST and XY stage 14 via the reticle stage drive unit 48 and wafer stage drive unit 56 based on the measured values of the laser interferometers 54 R and 54 W, respectively. The position and speed of are controlled respectively. That is, in the present embodiment, the reticle stage drive unit 48, the wafer stage drive unit 56, and the main controller 50 constitute a drive device that synchronously moves the reticle stage RST and the XY stage 14 in one-dimensional direction. ing. At the time of stepping, the main controller 50 controls the position of the XY stage 14 via the wafer stage drive unit 56 based on the measurement value of the laser interferometer 54W.

 In addition, the main controller 50 monitors the output of the integrator overnight sensor 46 in order to apply the target integrated exposure amount determined according to the exposure conditions and the resist sensitivity to the wafer W during the above-described scanning exposure. By supplying the control information TS to the light source 16, the oscillation frequency (light emission timing) and light emission power of the light source 16 are controlled, or the energy rough adjuster 20 is controlled via the motor 38. This adjusts the amount of light applied to the reticle R, that is, the amount of exposure. The main controller 50 controls the illumination system aperture stop plate 24 via the driving device 40, and further controls the opening and closing operation of the movable reticle blind 30B in synchronization with the operation information of the stage system. .

As described above, in the present embodiment, the main controller 50 also has a role of an exposure controller (exposure amount control system) and a stage controller (stage control system). Of course, these controllers may be provided separately from the main controller 50. Next, an exposure sequence when transferring a reticle pattern onto a predetermined number of wafers W (here, M = 100) in the exposure apparatus 10 of the present embodiment configured as described above will be described. The control algorithm of the CPU in the control device 50 will be described with reference to the flowchart of FIG.

 First, the preconditions will be described.

 ① Shot map data (shot data) based on the shot arrangement, shot size, exposure order of each shot, and other necessary data input from the input / output device 62 (see Fig. 1) such as a console by the operator. It is assumed that data defining the exposure order and scanning direction of each shot area) is created and stored in the memory 51 (see FIG. 1).

② The output DS of the integrator sensor 46 is calibrated in advance with the output of a reference illuminometer (not shown) installed on the Z tilt stage 58 at the same height as the image plane (ie, the surface of the wafer). Option). The data processing unit of the reference illuminometer is a physical quantity of (mJ Z (cm ² -pulse)). Calibration of the integration sensor 46 means that the output DS (digit / pulse) of the integration sensor 46 is calculated on the image plane. Conversion factor K 1 for converting to the exposure amount (mJ Z (cm ² -pulse))

(Or a transformation function). By using this conversion coefficient Κ1, it is possible to measure the amount of exposure given on the image plane indirectly from the output DS of the integration sensor 46.

 ③ In addition, the output ES of the energy monitor 16c is also calibrated with respect to the output DS of the integrator sensor 46 after the above calibration is completed, and the correlation coefficient の 2 between them is also obtained in advance. Is stored.

④ Further, the output of the reflected light monitor 47 is calibrated against the output of the integrator sensor 46 after the above calibration is completed, and the correlation coefficient between the output of the integrator sensor 46 and the output of the reflected light monitor 47 Κ 3 Is obtained in advance and stored in the memory 51. ⑤ Further, it is assumed that the memory 51 of FIG. 1 stores table data indicating the optical system transmittance measurement timing due to the difference in the exposure condition as shown in (Table 1) below. Also, the count value m of the first counter, which indicates the number of wafer exposures to be described later, is initially set to `` 1 J, '' and the count value n of the second count, which indicates the number of wafers processed in the transmittance measurement section, is initially set to `` 0. '' It is assumed that

 【table 1】

The control algorithm shown in Fig. 3 is started by the operator from the input / output device 62 (see Fig. 1) such as a reconsole to the illumination conditions (the numerical aperture N of the projection optical system, the coherence factor and the reticle pattern). (Including contact hole, line and space, etc.), reticle type (such as phase difference reticle, halftone reticle, etc.) and minimum line width or exposure tolerance are input. Accordingly, main controller 50 sets the aperture stop (not shown) of projection optical system PL, selects and sets the aperture of illumination system aperture stop plate 24, selects the dimming filter of energy rough adjuster 20, Set the target integrated exposure amount according to the resist sensitivity, and perform a series of preparation work such as reticle loading, reticle alignment, baseline measurement, etc. Is completed.

 First, in step 100, the transmittance R t (%) of the reticle R loaded on the reticle stage R ST is determined as follows. That is, first, the light source 16 emits pulse light and the shutter 16 f is opened, and the reticle R is irradiated by the exposure light E. At that time, the integrator sensor 46 and the reflected light module 4 are used. Take the output of 7 and multiply the ratio by the above correlation coefficient K3,

The transmittance R t (%) of the reticle R is obtained by subtracting 1 and multiplying by 100. At this time, since the X 丫 stage 14 is located at a predetermined opening away from immediately below the projection optical system PL, the XY stage 14 does not exist directly below the projection optical system PL. The reflected light from below can be considered negligibly small. In this case, in order to more accurately determine the reticle transmittance R t (%), the following may be performed.

 That is, the reticle R is provided with a barcode indicating information indicating the type of the reticle, the pattern density, the reticle pattern, and the reflectivity of the reticle itself (glass material). Main controller 50 reads the barcode of reticle R via a barcode reader (not shown) when reticle R is loaded onto reticle stage RST, and stores it in memory 51. Then, the main controller 50 irradiates the reticle R with the exposure light EL in the same manner as described above, captures the outputs of the integration sensor 46 and the reflected light monitor 47 at that time, and stores these outputs and the memory 5

Based on the reticle information in 1, the transmittance Rt (%) of the reticle R is determined. As still another method, the transmittance of all the reticles R loaded on the reticle stage R ST is measured, and the information of the transmittance is stored in a memory for each reticle.

Store it in 1. Then, in main controller 50, reticle stage R

The transmittance information corresponding to the reticle R loaded on the ST may be read from the memory 51 to determine the transmittance of the reticle R. In either case, after determining the reticle transmittance, close shirt f 16 f. In the next step 102, based on the exposure condition previously input by the operator and the reticle transmittance (%) obtained in the above step 100, the reticle transmittance (%) is stored in the memory 51 as described above (Table 1). By using the above table, the transmittance measurement interval of the optical system, specifically, the transmittance measurement interval of the optical system including the relay lenses 28A and 28B, the condenser lens 32, and the projection optical system PL is determined. Specifically, it is assumed that the transmittance measurement is performed every time exposure of N wafers is completed, and the N sheets are set to n 1 sheets. For example, if the minimum line width is 250 nm (0.25 m) or the exposure tolerance is 1.0% and the reticle transmittance is 30%, use the table in Table 1 to obtain N = n Set 1 (= 8) and store it in memory 51. For example, if the minimum line width is 250 nm (0.25 m) or the exposure tolerance is 1.0% and the reticle transmittance is 3%, N lots are used in one lot. That is, N = n 1 (= 25) is set assuming that one lot is 25 sheets and stored in the memory 51. In the following description, it is assumed that N = n 1 = 8.

In the next step 104, the transmittance of the optical system is measured as follows. That is, the X 丫 stage 14 is driven via the wafer stage drive unit 56 so that the irradiation amount monitor 59 is located immediately below the projection optical system PL, and the shutter 16 f is opened. This is performed by multiplying the ratio of the output of the integrator sensor 46 to the output of the irradiation amount monitor 59 by 100 and multiplying the ratio by a predetermined coefficient (K4). Then, an exposure amount control target value is set according to the measured transmittance of the optical system. In the next step 106, a wafer transfer system (not shown) is instructed to replace the wafer W. As a result, the wafer transfer system (or a wafer transfer mechanism, not shown) on the XY stage performs wafer exchange (in the case where there is no wafer on the stage, simple wafer opening). The so-called search and fine alignments disclosed in Japanese Patent Publication No. 9-118661 and Japanese Patent Application Laid-Open No. Hei 9-136202 and U.S. Pat. 1-Showa 44444 and corresponding US Patent Nos. 4,780,617, which are incorporated herein by reference, enhances the use of a statistical method using the least squares method to obtain the array coordinates of all the shot areas on the wafer W. · Global · alignment (EGA) etc. are processed in a series of alignment processes. These wafer exchange and wafer alignment are performed in the same manner as in a known exposure apparatus. To the extent permitted by the national laws of the designated or designated elected country in this international application, the disclosures in the above publications and the corresponding U.S. patent applications and U.S. patents are incorporated by reference and are incorporated in part of this specification. I do.

 In the next step 110, the wafer W is moved to a scanning start position for exposure of each shot area on the wafer W based on the alignment result and the shot map data in the above step 108. The reticle pattern is transferred to a plurality of shot areas on the wafer W by a step-and-scan method by repeating the operation and the above-described scanning exposure operation. During the scanning exposure, the above-described exposure control is performed by the main controller 50. At this time, the exposure control target value corresponding to the transmittance measured in step 104 and the integrator sensor 4 are controlled. Based on the output of 6, the exposure amount control is performed as described above.

 In this way, when the exposure of the m-th (here, the first) wafer W is completed, the process proceeds to step 112, where the count value m of the first counter and the second counter Increment the count value n by 1 (nn + 1, m <-m + 1).

 In the next step 114, it is determined whether or not the count value m has exceeded the planned number M of processed sheets. At the time when the exposure of the first wafer W is completed, since m = 2, this judgment is naturally denied, and the process proceeds to step 1 16 where the count value n is N, that is, n 1 = Judge whether it is 8. When the exposure of the first image is completed, n = 1, so that this determination is denied, and the process returns to step 106 to repeat the above processing and determination.

Then, when the exposure of the eighth wafer is completed, n = 8 = N, and the step Step 1 16 is affirmed, the process proceeds to step 1 18 to reset the second counter (n−0), and then returns to step 104 to measure the transmittance of the optical system in the same manner as described above. Then, the measurement result is stored in the memory 51, that is, the measured value of the transmittance is updated.

 Thereafter, the processing and judgment of step 106 and subsequent steps are repeated, and every time eight wafers are exposed, the transmittance measurement of the optical system is repeated, and when the exposure of the 100th wafer is completed, When the determination in step No. 14 is affirmed, a series of exposure processing ends.

 As is clear from the above description, in this embodiment, the transmittance measuring device is configured by the integrator sensor 46, the irradiation amount monitor 59, and the main controller 50. The functions of the main controller 50 realize an exposure amount setting device and an exposure amount control system.

As described above, according to the present embodiment, the main controller 50 controls the optical system (including the relay lenses 28A and 28B, the condenser lens 32, and the projection optical system PL) according to the exposure conditions. ), Set the transmittance measurement interval (step No. 0 2), and execute the transmittance measurement at the set measurement interval (steps No. 04 to 116). That is, at a predetermined timing according to the exposure condition, the main controller 50 detects the amount of exposure light passing through the optical system using the irradiation amount monitor 59 on the Z stage 58, and The transmittance of the optical system is determined based on the light amount and the output of the integrator sensor 46, and the exposure value control target value is updated (set) according to the determined transmittance. Until the next transmittance measurement, the exposure is controlled based on the exposure control target value corresponding to the transmittance measured before and the output of the integrator sensor 46, The pattern of the reticle R illuminated with the exposure light from the light source 16 is transferred onto the wafer W via the projection optical system. As described above, according to the exposure apparatus 10 of the present embodiment, while measuring the transmittance of the optical system at measurement intervals set according to the exposure conditions, the exposure amount is determined based on the actually measured transmittance. Is controlled, so it depends on the exposure conditions. In addition, the illuminance of the wafer surface (image surface illuminance) can always be set to a desired (appropriate) value without being affected by the fluctuation of the transmittance of the optical system, and high-precision exposure can be realized. Also, no complicated calculation for estimating the transmittance is required.

 Further, in the present embodiment, the main controller 50 automatically determines the interval for measuring the transmittance of the optical system according to the reticle transmittance Rt and the minimum line width (or the exposure tolerance). (See Table 1) for the following reasons. In other words, when the reticle transmittance Rt is low, the amount of change in the transmittance of the projection optical system PL or the like is small, so that the interval of transmittance measurement of the optical system may be made longer, and conversely, the reticle transmittance This is because, when Rt is high, the amount of change in the transmittance of the projection optical system PL and the like becomes large, and it is considered that it is better to shorten the interval of transmittance measurement of the optical system. In addition, the reason why the minimum line width is considered is that, depending on the layer (layer) to be exposed, there are cases where accuracy is important and cases where processing speed is important. In summary, in this embodiment, while maintaining the exposure accuracy sufficiently high, the transmittance of the optical system is set based on the reticle transmittance Rt and the minimum line width from the viewpoint of as high a throughput as possible. The measurement interval (timing) is determined.

However, the present invention is not limited to this. That is, the transmittance of the optical system depends on the illumination system N.A. and the projection optical system N., the coherence factor, the type of reticle (phase difference reticle, etc.), the reticle pattern (contact hole, periodic pattern). It is known that the behavior differs depending on various conditions (exposure conditions in a broad sense) such as reticle transmittance Rt, minimum line width (or exposure tolerance), and each of these exposure conditions. It goes without saying that the interval at which the transmittance of the optical system is measured may be automatically determined according to any combination of the above. For example, when automatically setting the optical system transmittance measurement interval according to the type of reticle, reticle pattern, etc., the information such as the reticle type is recorded on a part of the reticle with a barcode, etc. This is read by a bar code reader or the like during loading of the reticle, and when the main controller 50 recognizes the reticle type, etc., the measurement interval Can be set automatically. A method of recording information such as the type of the reticle on a part of the reticle with a bar code or the like and reading the reticle with a bar code reader or the like while the reticle is being loaded is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-148282 It is disclosed in detail in reports.

 By the way, in the above embodiment, the transmittance measurement interval of the optical system is determined according to the determined exposure condition, in other words, the optical system is determined at the interval determined for each exposure condition, for example, for each lot, for each predetermined number of sheets, or the like. The case where the transmittance measurement is repeatedly performed has been described. However, when the exposure is performed continuously, the transmittance variation of the projection optical system PL and the like is not uniform. It is considered more desirable to automatically change the interval of the optical system transmittance measurement in accordance with the embodiment. The following second embodiment focuses on this point.

 << 2nd Embodiment >>

 Next, a second embodiment of the present invention will be described with reference to FIG. Here, the same reference numerals are used for the same or equivalent components as those of the first embodiment, and the description thereof is omitted. The second embodiment has the same device configuration and the like as the above-described first embodiment, and differs from the first embodiment only in the function of main controller 50. Therefore, the following description will focus on this point.

FIG. 4 shows a flowchart corresponding to a main control algorithm of main controller 50 according to the second embodiment. An exposure sequence when a reticle pattern is transferred onto a predetermined number of wafers (here, M = 1100) W by the exposure apparatus of the second embodiment will be described with reference to FIG. . As a prerequisite, similarly to the first embodiment described above, the shot map data is stored in the memory 51 (see FIG. 1) in advance, and the output of the integrator sensor 46 is compared with the reference illuminometer output. It is assumed that the calibration of the output of the energy monitor 16 c and the output of the reflected light monitor 47 for the output of the integration sensor 46 having completed the calibration and this calibration has been completed. Ma In addition, the count value n of the first count indicating the number of wafer exposure processing described later is initially set to 门 '', and the count value n of the second counter indicating the number of wafers corresponding to the transmittance measurement interval is initialized to `` 0 ''. It is assumed that In this case, it is assumed that the transmittance Rt of the reticle R used for exposure is measured in advance.

 The control algorithm in Fig. 4 starts when the operator uses the input / output device 62 (see Fig. 1) such as a recon- troller to expose the lighting conditions, reticle pattern type, reticle type, and minimum line width. The conditions are input, and in response to this input, the main controller 50 sets the aperture stop (not shown) of the projection optical system PL, selects and sets the aperture of the illumination system aperture stop plate 24, and sets the energy rough adjuster 2 This is the point at which a series of preparatory operations such as reticle loading, reticle alignment, baseline measurement, etc. are completed, such as selecting the darkening filter of 0, setting the target integrated exposure amount according to the resist sensitivity, etc. And

 Also, in the following, the transmittance measurement interval of the optical system is set to 1 wafer, 5 wafers, 10 wafers, 25 wafers (1 lot), 50 wafers (2 lots), and 100 wafers. It is assumed that the number (measurement interval) of each number (measurement interval) is expressed as X i (i = 1, 2, 3, 4, 5, 6) for convenience, as it is changed to six steps for each number (4 lots).

Here, as the default setting, the measurement interval of the optical system transmittance is set to one lot, that is, N = X ₄ = 25, and the exposure tolerance (here, the optical system transmittance change allowable value and Match) is set to 1%. In step 200, similarly to step 104 described above, the XY stage 14 is driven via the wafer stage drive unit 56 so that the irradiation amount monitor 59 is located immediately below the projection optical system PL. When the shirt 16 f is opened, the ratio between the output of the integrator sensor 46 at this time and the output of the irradiation amount monitor 59 is multiplied by 100 and a predetermined coefficient (K4) is set. By multiplying, the transmittance of the optical system is measured, and the result is stored in the temporary storage area of the RAM.

In the next step 202, it is determined whether the count value m of the first counter is Γ1 ”. Judge. Before the exposure of the first wafer W, since m = 1, this determination is affirmed, and the process proceeds to step 204 and the transmittance of the optical system stored in the temporary storage area in step 200 above. Is stored in a predetermined area of the memory 51.

 Then, in steps 2 19, 2 0, 2 2 4, 2 2 6 and 2 2 8, the same processing and judgment as in steps 10 6 to 1 16 in FIG. The second to fifth wafers W are sequentially exposed. Then, when the exposure of the last wafer W in one lot is completed, n = 25 = N, and the judgment in step 228 is affirmed. The process proceeds to step 230 to reset the second counter (n— 0), return to step 200, measure the transmittance of the optical system in the same manner as described above, store the result in the temporary storage area of the RAM, and proceed to step 202.

 In this step 202, it is determined whether or not the count value m of the first counter is ΠJ. At this time, since m = 26, this determination is denied and the process proceeds to step 206. Transition.

In this step 206, the difference between the current transmittance stored in the temporary storage area in the RAM and the previous transmittance stored in the predetermined area in the memory 51 (change in transmittance) Is calculated, this calculation result is stored in another area in the RAM, and a predetermined area in the memory 51 is overwritten with the current transmittance to update the transmittance. In the next step 208, it is determined whether or not the change in the transmittance calculated in the above step 206 is within 0.5%. If this determination is affirmed, the process proceeds to step 210 to determine whether or not the subscript i of Xi that defines the transmittance measurement interval of the optical system is 6. In this case, since N = 2 5 = X ₄ , that is, ί = 4, the determination in step 210 is denied, and the process proceeds to step 212 to update Ν = X _{i + 1} . In this case, it is updated to N = X ₅ = 50, regularly spaced measuring the transmittance of the optical system is changed every two lots from each batch. Then, the process proceeds to step 219 to perform exposure on two lots of wafers W.

On the other hand, if step 2 1 0 positive judgment is made, i.e., N = X ₆ = 1 0 0 If the transmittance change is within 0.5%, the longest transmittance measurement interval is every 100 wafers in the present embodiment, so that step 2 19 The measurement of the transmittance is repeated every time the exposure of the wafer W of four lots is completed.

On the other hand, if the determination in step 208 is denied, that is, if the amount of change in the transmittance calculated in step 206 exceeds 0.5%, the process proceeds to step 214. It is determined whether or not the transmittance change is within 1%. If this judgment is affirmed, the process proceeds to step 2 19 as it is within the tolerance of the default change in transmittance. For example, when N = 25 = X 4, Exposure is performed on one lot of wafers W. On the other hand, if the determination in step 214 is negative, that is, if the amount of change in the transmittance calculated in step 206 exceeds 1%, the process proceeds to step 214 and the optical system It is determined whether or not the subscript の of X i that defines the transmittance measurement interval is “1”. Here, assuming that Ν = 2 5 = Χ ₄ , that is, i = 4, the judgment in step 2 16 is denied, and the process proceeds to step 2 18 to update Ν = Χ _Η . In this case, Ν = Χ ₃ = 10 is updated, and the transmittance measurement interval of the optical system is changed from every lot to every 10 sheets. After that, the flow shifts to step 219 to expose the 10 wafers W.

 On the other hand, if the judgment in the step 2 16 is affirmative, that is, if Ν = Χ, = 1 and the change in transmittance exceeds 1%, the shortest transmittance measurement is performed. Despite the setting of the interval, the change in transmittance exceeds the allowable value, and if the exposure is continued as it is, the exposure with the required accuracy cannot be performed. A warning is issued to the operator by the illustrated buzzer or the like, and the exposure operation is forcibly terminated. This is because such a situation is caused by some abnormality.

According to the above-described exposure processing routine, exposure is sequentially performed on the wafer W. However, unless the process is forcibly terminated halfway, the wafer W of the 40th lot is exposed, and when the exposure of the 100th wafer W is completed, m = 1001 is reached. When the determination in step 226 is affirmed, a series of exposure processing operations ends. Here, during the scanning exposure in step 222, the main controller 50 performs the exposure control target value according to the transmittance measured in step 200, similarly to the first embodiment described above. Of course, the exposure control is performed based on the output of the integrator sensor 46 as described above.

 According to the second embodiment described above, the transmittance measurement of the optical system is executed at predetermined measurement intervals, and the exposure is controlled based on the actually measured transmittance. It is possible to always set the illuminance on the wafer surface (image surface illuminance) to a desired (appropriate) value without performing complicated calculations for exposure. In addition, according to the second embodiment, the transmittance measurement in the next and subsequent times is performed according to the amount of change between the transmittance obtained in the transmittance measurement immediately before and the transmittance obtained in the transmittance measurement before that. Since the interval is changed, the transmittance measurement interval should be shortened during periods where the transmittance must be measured frequently and where the rate of change of the transmittance is large, and vice versa. In addition, high-precision exposure control can be realized without unnecessarily lowering the throughput.

 In the second embodiment, the case where the measurement interval of the transmittance is changed based on the variation of the transmittance of the optical system obtained after the start of the actual exposure has been described. The transmittance of the optical system may be measured two or more times before the start, and the measurement interval may be automatically set based on the difference.

Further, in the above embodiment, the case where the exposure apparatus automatically sets the measurement interval of the optical system transmittance according to the exposure condition is described. However, the operator automatically sets the measurement interval according to the exposure condition and the like. May be set. Similarly, the optical system transmittance measured during the exposure can be displayed on a display or the like, and the operator can set the transmittance measurement interval based on the display. In the above embodiment, as the exposure amount control method, the target integrated exposure amount determined according to the exposure condition and the resist sensitivity is given to the wafer W during the scanning exposure. (Emission timing) and emission power are controlled, or the dimming rate is adjusted by the energy coarse adjuster 20.However, in the case of a scanning type exposure apparatus, when the scanning exposure is performed, It is also possible to adjust the exposure amount by changing the scanning speed while keeping the power of the light source 16 constant and maintaining the speed ratio between the reticle stage RST and the XY stage 14. It is possible. Alternatively, the exposure amount can be controlled by controlling the movable reticle blind 30 B in the illumination optical system 12 and changing the width (so-called slit width) of the illumination area 42 R in the scanning direction. Can be. Alternatively, it is also possible to adjust the exposure amount by combining the adjustment of the scanning speed and the adjustment of the slit width.

 In any case, since the illuminance on the wafer surface is affected by the fluctuation of the transmittance of the projection optical system PL and the like, the exposure amount is controlled so that this effect is canceled out and the target integrated exposure amount is always given to the wafer W. The target values (control target values such as pulse oscillation frequency, pulse energy, extinction rate, scanning speed, slit width, etc.) may be updated. For the same purpose, when the exposure condition is changed, it is desirable to measure the transmittance and to update the exposure control target value according to the measured transmittance. In addition, since the manner in which the transmittance varies varies depending on the exposure conditions, it is desirable to set the transmittance measurement interval in accordance with the exposure conditions.

 << Third embodiment >>

 Next, a third embodiment of the present invention will be described with reference to FIGS. Here, the same reference numerals are used for the same or equivalent components as those of the first embodiment, and the description thereof will be simplified or omitted.

FIG. 5 shows a schematic configuration of an exposure apparatus 10 ′ of the third embodiment. This exposure apparatus 10 ′ uses an Ar F excimer laser light source (oscillation wavelength 1 This is a step-and-scan type scanning exposure apparatus using 93 nm). The exposure apparatus 10 ′ has the same basic configuration as the above-described exposure apparatus 10, but includes an internal environment sensor 53 for measuring a predetermined physical quantity in a lens chamber inside the projection optical system PL, and a projection optical system. An external environment sensor 49 for measuring a predetermined physical quantity in the chamber 11 outside the system PL is further provided, and an exposure amount control method and a transmittance prerequisite for the exposure amount control are obtained. Since these are different from the above embodiments, the following description will focus on these points.

The internal environment sensor 5 3, the combined sensor comprising a pressure sensor and C 0 ₂ gas sensor for measuring the concentration used to measure the pressure of the lens chamber, and as the external environment sensor 4 9, the chamber 1 1 A composite sensor consisting of a temperature sensor for measuring temperature and a humidity sensor for measuring humidity shall be used. The outputs of the external environment sensor 49 and the internal environment sensor 53 are supplied to the main controller 50.

 The configuration of the other parts is the same as that of the above-described first embodiment, except for the configuration of main controller 50 and the function related to control of the exposure amount, which will be described next.

Next, in the exposure apparatus 100 ′ of the third embodiment, after the operation of the apparatus is stopped, the operation of the apparatus is started next, and a predetermined number of sheets (M sheets, for example, M = 100) A sequence until the reticle pattern is transferred onto the wafer W and the operation of the apparatus is stopped again will be described with reference to the flowcharts of FIGS. Here, it is assumed that main controller 50 is mainly configured with three processors of a first processor, a second processor, and a third processor. Among them, the second processor repeatedly samples the measurement values of the external environment sensor 49, the internal environment sensor 53, the integrator sensor 46, etc. at a predetermined time Δt, for example, every one minute, and stores the data in the memory 51. It has the function of recording in a predetermined area together with the sampling time. Further, the third processor has a function of calculating a predicted value of a temporal change in the transmittance of the optical system at a predetermined time interval at the time of exposure described later. 1st processor The W51S is a main processor that performs processing according to the control algorithm shown in the flowcharts of FIGS.

First, when the operation of the device is stopped in step 300, the process proceeds to step 302 and the time measured by a timer (not shown) at the time when the operation of the device is stopped is fetched and stored in the temporary storage area of the TRAM. Accordingly, the temperature of the chamber 1 1 in the measurement and stopping the operation stop elapsed time starts humidity, and the lens room pressure, the measured total of C 0 ₂ concentration.

In the next step 304, the process waits for an operation start instruction to be input. During this operation stop period, the measurement values of the external environment sensor 49 and the internal environment sensor 53 are stored in the memory 51 together with the time at one minute intervals by the second processor described above. When the operation start instruction is input, the process proceeds to Step 3 0 6, the temperature of the chamber 1 1 in the measurement and stop of the operation stop elapsed time, humidity, and the lens room air pressure, C 0 ₂ concentration The measurement of is ended. Specifically, the time measured by a timer (not shown) at the time when the operation start instruction is input is fetched and stored in the temporary storage area of the RAM, and the time fetched in step 302 and the time fetched in step 303 are taken. The data of the embedded time and the measurement values of the external environment sensor 49 and the internal environment sensor 53 corresponding to the time between these times are read out from the memory 51, and read out from a predetermined area in the RAM (hereinafter referred to as “first measurement”). Data storage area).

In the next step 308, after moving the XY stage 14 so that the irradiation dose monitor 59 is located immediately below the projection optical system PL, laser oscillation from the light source 16 is started and the shirt And start self-cleaning (run-in operation). At the same time, the time measured by the timer (not shown) at the time when self-cleaning was started in step 110 is captured and stored in the temporary storage area of the RAM, so that the elapsed time during self-cleaning and various sensors can be measured. Start measurement by. Here, the self-cleaning is performed because the change in the transmittance of the optical system becomes smaller as the amount of exposure light to the optical system becomes larger. This is because a change in transmittance of the optical system can be reduced.

 In the next step 312, wait for the self-cleaning to end. The determination of the end of the self-cleaning is performed as follows. That is, during self-cleaning, the amount of change in the ratio between the output of the integration sensor 46 and the output of the irradiation amount monitor 59 is measured, and when the amount of change disappears or the amount of change reaches a predetermined level. Judge that self-cleaning is complete. During the self-cleaning period, the measured values of the integrator sensor 46, the external environment sensor 49, and the internal environment sensor 53 are stored in the memory 51 together with the time at one-minute intervals by the second processor.

When it is determined that the self-cleaning is completed as described above, the process proceeds to step 3 14 to close the shutter 16 f and display the completion of the self-cleaning on a display (not shown), and then proceeds to step 3 16. The measurement of elapsed time of self-cleaning and the measurement by various sensors during self-cleaning are completed. Specifically, the time measured by the timer (not shown) at the time of closing the shutter 16 f is acquired and stored in the temporary storage area of the RAM, and the time acquired in step 310 and the time acquired in step 310 are obtained. Data from the integrated time sensor 46, the external environment sensor 49, and the internal environment sensor 53 corresponding to the data at the specified time and the time between these times are read out from the memory 51, and read out from a predetermined area in the RAM (hereinafter referred to as “ 2nd measurement data storage area). In the next step 318, it waits for the input of the exposure condition. Then, the operator inputs illumination conditions (numerical aperture (N., coherence factor) of the projection optical system, type of reticle pattern (contact hole, line and space) from an input / output device 62 (see FIG. 1) such as a console. Etc.), reticle transmittance, reticle type (phase difference reticle, half-tone reticle, etc.), and exposure conditions including minimum line width or exposure tolerance, etc., are entered. Set the aperture stop (not shown) of the projection optical system PL, select the aperture of the illumination system aperture stop plate 24, select the neutral density filter of the energy rough adjuster 20, and set the target integrated exposure amount according to the resist sensitivity. Make settings, etc., and furthermore, reticle load, reticle alignment, baseline After performing a series of preparation work such as measurement, the process proceeds to the subroutine for the exposure processing in step 3. Here, the reticle transmittance is measured in advance as follows. That is, the light source 16 emits pulse light and the shirt light 16 f is opened, the reticle R is irradiated with the exposure light EL, and the outputs of the integrator light sensor 46 and the reflected light monitor 47 at that time are captured. The transmittance (%) of the reticle R is obtained by multiplying the ratio between the two by a predetermined correlation coefficient, subtracting this from 1 and multiplying it by 100. At this time, since the XY stage 14 is located at a predetermined loading position distant from directly below the projection optical system PL and does not exist immediately below the projection optical system PL, the reflected light from below the projection optical system PL is ignored. Think of it as small as possible.

 In the subroutine of step 322, as shown in FIG. 7, in step 328, the optical system is set based on the data in the first and second measurement data storage areas in ^ 1 and the exposure conditions at that time. (Transmission lens 28A, 28B, condenser lens 32, optical system composed of projection optical system PL) is determined, and a function for estimating the change with time of transmittance is given to the third processor. Specifically, the above-mentioned prediction function is determined by obtaining the irradiation history of the exposure light to the optical system using the data in the first and second measurement data storage areas in the RAM, Based on the measured values of various sensors during and during self-cleaning, for example, the parameter a in the following equation (1) is determined, and based on the exposure conditions input in step 3 18, the following equation (1) ) Is determined by determining the parameters bi (i = 1, 2, …… k).丄, = a · exp ∑ b it (1)

 V 1

 Where T is the transmittance of the optical system, that is, the ratio of the illuminance of the exposure light emitted from the light source to the illuminance of the exposure light on the substrate surface that has passed through the optical system.

a: Parameter indicating the rate of change bi: Parameters that depend on each exposure condition, including illumination conditions such as the dimming rate and coherence factor

 In the next step 330, the count value m of the first counter indicating the number of wafer exposure processing described later is set to “1”, and the count value n of the second counter indicating the number of wafers corresponding to the transmittance measurement interval is set to n. Initially set to "0". Here, it is assumed that the transmittance measurement is performed each time one slot, that is, 25 wafers, is exposed, that is, N = 25 described later.

 In the next step 332, the transmittance of the optical system is measured as follows. That is, the XY stage 14 is driven via the wafer stage drive unit 56 so that the irradiation amount monitor 59 is located immediately below the projection optical system PL, and the shirt 16 f is opened. This is performed by multiplying the ratio between the output of the integrator sensor 46 at this time and the output of the irradiation amount monitor 59 by 100 and multiplying the ratio by a predetermined coefficient. When an unevenness sensor is used instead of the irradiation amount monitor 59, it is necessary to perform transmittance measurement by positioning the unevenness sensor on the optical axis of the projection optical system PL.

 In the next step 334, the measurement result of the transmittance is given to the third processor, and the start of the prediction calculation of the time change of the transmittance is instructed. As a result, the third processor uses the given transmittance as an initial value and starts predictive calculation of the transmittance time change for each predetermined time At1. It is assumed that the calculation result is sequentially updated and stored in a predetermined area (referred to as “transmittance data storage area”) in the memory 51 by the third processor.

In the next step 336, replacement of the wafer W is instructed to a wafer transfer system (not shown). As a result, the wafer is exchanged (or, if there is no wafer on the stage, simply a wafer slot) by the wafer transfer system and a wafer transfer mechanism (not shown) on the XY stage. A series of alignment steps such as a license and a fine alignment (eg, EGA described above) are performed. These wafer exchanges and wafer alignments are performed using a known exposure device. Is performed in the same manner as described above.

 In the next step 340, the latest predicted calculated value of the transmittance at that time is read from the transmittance data storage area in the memory 51, and the exposure light control target value is updated based on the transmittance. Then, proceeding to the next step 342, the scanning start position for exposure of each shot area on the wafer W is determined based on the alignment result of the above step 338 and predetermined shot map data. The reticle pattern is transferred to a plurality of shot areas on the wafer W by a step-and-scan method by repeatedly performing the operation of moving the wafer W and the above-described scanning exposure operation. During the scanning exposure, the exposure control is performed as described above based on the exposure control target value corresponding to the transmittance and the output of the integrator sensor 46. In this way, when the exposure for the m-th wafer (here, the first wafer) W is completed, the process proceeds to step 344, where the count value m of the first counter and the second counter Increment the count value n by 1 (n-n + l, m «-m + 1).

 In the next step 346, it is determined whether or not the count value m has exceeded the planned processing number M. At the time when the exposure of the first wafer W is completed, since m = 2, this judgment is naturally denied, and the process proceeds to step 348, where the count value n is N, that is, 25. It is determined whether or not there is. When the exposure of the first image is completed, this determination is denied because n = 1, and the process returns to step 336 to repeat the above-described processing and determination.

Then, when the exposure of the second and fifth wafers is completed, n = 25 = N, and the judgment in step 348 is affirmed. The process proceeds to step 350 to reset the second counter (n 0), return to step 332, measure the transmittance of the optical system in the same manner as described above, give the measurement result as the initial value to the third processor, and perform the prediction calculation of the transmittance time change. Instruct to start. As described above, in the present embodiment, the measurement data of the transmittance measured each time the exposure of one lot of the wafer is completed is performed by the third processor. By giving the initial value to the processor, the deviation of the calculated transmittance prediction result is corrected.

 Thereafter, the above processing and judgment are repeated, and every time when exposure of 25 wafers is performed, the transmittance measurement of the optical system is repeatedly performed. The determination is affirmed, and the process returns to step 300 of the main routine in FIG. Stopping the apparatus in step 300 means turning off the light source 16 and giving an instruction to end the measurement to the third processor. Ends.

 As is clear from the above description, in the third embodiment, the functions of the main control device 50 implement an exposure amount setting device, an exposure amount control system, and an arithmetic device.

 As described above, according to the third embodiment, the irradiation history of the exposure light to the optical system (the optical system including the relay lenses 28A and 28B, the condenser lens 32, and the projection optical system PL). However, a function for predicting the time change of the transmittance of the optical system in accordance with the actual exposure conditions is determined, and the amount of exposure light is predicted and controlled based on the determined function for predicting the time change of the transmittance. The pattern of the reticle R can be transferred onto the wafer W using an optical system while the image plane illuminance (wafer plane illuminance) is always set to a substantially desired value. Therefore, high-precision exposure can be realized without being affected by a change in the transmittance of the optical system.

Also, since the transmittance is measured every time one lot of exposure is completed, it is compared with the case where the transmittance is measured before each exposure to determine the time change characteristics of the transmittance. However, the throughput can be kept high. Furthermore, since the transmittance time change prediction result is corrected each time transmittance is measured, unlike the case where the transmittance is completely calculated, the error in the exposure value predicted during the transmittance measurement is different. Is corrected for each lot, enabling more accurate exposure control. In the third embodiment, the exposure light is controlled by applying the target integrated exposure dose determined according to the exposure conditions and the resist sensitivity to the wafer W during scanning exposure. The case where the frequency (light emission timing), the light emission power, and the like are controlled or the dimming rate by the energy coarse adjuster 20 is adjusted has been described. Similarly, during scanning exposure, the scanning speed may be changed while the power of the light source〗 6 is kept constant and the speed ratio between the reticle stage RS and the X 丫 stage 14 is maintained. The exposure amount may be adjusted by changing the slit width, or by combining the scanning speed adjustment and the slit width adjustment.

 In any case, since the illuminance on the wafer surface is affected by changes in the transmittance of the projection optical system PL and the like, the exposure control is performed so that this effect is canceled out and the target integrated exposure is always given to the wafer W. The target values (control target values such as pulse oscillation frequency, pulse energy, extinction rate, scanning speed, slit width, etc.) may be updated.

 In the third embodiment, the case where the main controller 50 includes the first processor, the second processor, and the third processor has been described. Alternatively, the functions of the above-described first to third processors are realized by using a stage controller, an exposure controller, a lens controller, and the like under the control of the multi-task processing by the workstation or the time-division processing. Of course, it is also good.

 By the way, in the third embodiment, the case where the transmittance measurement of the optical system is repeatedly performed for each lot has been described. However, when the exposure is performed continuously, the projection optical system PL or the like is used. Since the mode of the transmittance change is not uniform, the interval of the optical system transmittance measurement is automatically changed according to the mode of the transmittance change in the same manner as in the second embodiment described above. May be.

Further, in the above embodiment, 25 pieces per lot are used, but 50 pieces or 100 pieces may be used. In the above embodiment, the time change prediction function of the transmittance of the optical system is determined according to the irradiation history of the exposure light and the set exposure condition. However, the exposure condition at the time of self-cleaning and the exposure condition after the start of exposure are determined. If are the same, the time change prediction function may be determined according to the irradiation history without considering the exposure condition.

 In each of the above embodiments, the case where the transmittance is measured every time a predetermined number of wafers are exposed has been described. However, the present invention is not limited to this, and the transmittance may be set every time a predetermined number of shots are completed. Of course, it may be possible.

 As described above, the exposure apparatus according to each of the embodiments described above performs various types of subsystems including the components (elements) recited in the claims (cla ims) of the present application with predetermined mechanical accuracy and electrical characteristics. It is manufactured by assembling to maintain the precision and optical precision. Before and after this assembly, adjustments to achieve optical accuracy for various optical systems, adjustments to achieve mechanical accuracy for various mechanical systems, and various electrical The system is adjusted to achieve electrical accuracy. The process of assembling the exposure apparatus from various subsystems includes mechanical connection, wiring connection of electric circuits, and piping connection of pneumatic circuits among the various subsystems. It goes without saying that there is an individual assembly process for each subsystem before the assembly process from these various subsystems to the exposure apparatus. When the process of assembling the various subsystems into the exposure apparatus is completed, comprehensive adjustments are made to ensure the various accuracy of the entire exposure apparatus. It is desirable to manufacture the exposure apparatus in a clean room where the temperature, cleanliness, etc. are controlled.

 In each of the above embodiments, the case where the present invention is applied to a step-and-scan type scanning exposure apparatus has been described. However, the scope of the present invention is not limited to this, and a stepper or the like may be used. The present invention can be suitably applied to the static exposure type exposure apparatus.

In each of the above embodiments, in each of the above embodiments, the present invention uses the ArF excimer laser light (wavelength: 193 nm), the KrF The description has been given of the case where the present invention is applied to an exposure apparatus using an excimer laser beam such as a laser beam (wavelength: 248 nm) or an F ₂ excimer laser beam (wavelength: 157 ηm). The present invention can also be suitably applied to an exposure apparatus that uses vacuum ultraviolet light such as Kr ₂ laser light or Ar ₂ laser light having a wavelength of 126 nm. In addition, a single-wavelength laser beam in the infrared or visible range oscillated from a DFB semiconductor laser or a fiber laser is amplified by, for example, a fiber amplifier doped with erbium (or both erbium and yttrium). Alternatively, a harmonic converted into a wavelength of ultraviolet light using a nonlinear optical crystal may be used.

For example, if the oscillation wavelength of a single-wavelength laser is in the range of 1.51 to .59 m, the 8th harmonic whose generation wavelength is in the range of 189 to 199 nm, or the generated wavelength is The 10th harmonic within the range of 151-159 nm is output. In particular, if the oscillation wavelength is in the range of 1.544 to 1.553 m, the 8th harmonic whose generation wavelength is in the range of 193 to 194 nm, that is, the ultraviolet light that has almost the same wavelength as the ArF excimer laser light light is obtained, when the range of the oscillation wavelength 1. 57~1. 58 m, 1 0 harmonic in the range of 1 57 to "! 58门occurs wavelength, i.e. Ho and F ₂ laser beam URN Ultraviolet light having the same wavelength is obtained.

If the oscillation wavelength is in the range of 1.03 to 1.12 m, a 7th harmonic whose output wavelength is in the range of 147 to 160 nm is output, and especially the oscillation wavelength is 1.099-m. 1. When 1 06 within the range of m, 7 harmonic generation wavelength falls within the range of 1 from 57 to 1 58 m, i.e., ultraviolet light having almost the same wavelength as F ₂ laser light. In this case, as the single-wavelength oscillation laser, for example, it is possible to use an indium-doped fiber laser.

Note that the projection optical system and the illumination optical system described in the first and second embodiments are merely examples, and the present invention is not limited thereto. For example, the projection optical system is not limited to the refractive optical system, but may be a reflective system composed of only a reflective optical element, or a catadioptric system having a reflective optical element and a refractive optical element. W5) may be used. In an exposure apparatus that uses vacuum ultraviolet light (VUV light) with a wavelength of about 200 nm or less, a catadioptric system may be used as the projection optical system. Examples of the catadioptric projection optical system include, for example, Japanese Patent Application Laid-Open No. Hei 8-171504 and U.S. Pat. No. 5,668,672 corresponding thereto, and Japanese Patent Application Laid-Open No. Hei 10-21095 and A catadioptric system having a beam splitter and a concave mirror as a reflecting optical element disclosed in U.S. Pat. No. 5,835,275 and the like corresponding thereto, or JP-A-8-334695 and a corresponding U.S. Pat. No. 5,689,377, and Japanese Patent Application Laid-Open No. Hei 10-3039 and corresponding US Patent Application No. 873,605 (filing date: June 12, 1999). As a reflection optical element, a reflection refraction system having a concave mirror or the like can be used without using a beam splitter. To the extent permitted by the national laws of the designated country designated in this international application or of the selected selected country, the disclosures in this specification are incorporated by reference to the disclosures in the above publications and U.S. patents corresponding thereto and U.S. patent applications. Partial. In addition, a plurality of refractive optical elements and two mirrors (U.S. Pat. Nos. 5,031,976, 5,488,229, and 5,717,518) disclosed in U.S. Pat. A primary mirror, which is a concave mirror, and a sub-mirror, which is a back mirror having a reflecting surface formed on the opposite side of the refracting element or the plane of incidence of the plane-parallel plate) on the same axis; A catadioptric system may be used that re-images the intermediate image of the reticle pattern formed on the wafer by the primary mirror and the secondary mirror. In this catadioptric system, a primary mirror and a secondary mirror are arranged following a plurality of refractive optical elements, and the illumination light passes through a part of the primary mirror and is reflected in the order of the secondary mirror and the primary mirror. It will pass through the part and onto the wafer. To the extent permitted by the national laws of the designated State or selected elected States in this International Application, the disclosures in the above US patents will be incorporated by reference. The variation in the transmittance of the optical system is defined as the optical elements (lenses 28A, 28B, 32, the projection optical system P, the mirror M) that are arranged between the integrator sensor 46 and the illuminance sensor 59. Surface), the fluctuation of the amount of exposure light passing through the surface. Therefore, the transmittance of the optical system according to the present invention includes, for example, a change in the reflectance of the mirror M in FIGS.

 When a reflection system or a catadioptric system is adopted as the projection optical system, the transmittance of the optical system according to the present invention naturally includes the reflectance of the reflection mirror. It is used not only for the exposure apparatus used for manufacturing semiconductor elements, but also for the manufacture of displays including liquid crystal display elements, etc., and for the manufacture of exposure apparatuses for transferring device patterns onto glass plates and for manufacturing thin film magnetic heads. The present invention can also be applied to an exposure apparatus that transfers a device pattern onto a ceramic wafer, an exposure apparatus that is used for manufacturing an imaging device (such as a CCD), and the like.

 《Device manufacturing method》

 Next, an embodiment of a device manufacturing method using the above-described lithography system (exposure apparatus) and exposure method in the Lisodara Fie process will be described.

 FIG. 8 shows a flowchart of an example of manufacturing devices (semiconductor chips such as IC and LSI, liquid crystal panels, CCDs, thin-film magnetic heads, micromachines, etc.). As shown in FIG. 8, first, in step 401 (design step), a function and performance design of a device (for example, a circuit design of a semiconductor device) is performed, and a pattern design for realizing the function is performed. . Subsequently, in step 402 (mask manufacturing step), a mask on which the designed circuit pattern is formed is manufactured. On the other hand, in step 400 (wafer manufacturing step), a wafer is manufactured using a material such as silicon.

Next, in step 404 (wafer processing step), using the mask and the wafer prepared in step 401 to step 403, an actual circuit is formed on the wafer by lithography technology or the like as described later. Etc. are formed. Next, in step 405 (device assembling step), device assembly is performed using the wafer processed in step 404. In this step 405, processes such as a dicing process, a bonding process, and a packaging process (chip encapsulation) are required. Included accordingly.

 Finally, in step 406 (inspection step), an operation confirmation test, a durability test, and the like of the device fabricated in step 405 are performed. After these steps, the device is completed and shipped.

 FIG. 9 shows a detailed flow example of step 404 in the case of a semiconductor device. In FIG. 16, in step 4 11 (oxidation step), the surface of the wafer is oxidized. In Step 4 1 2 (CVD step), an insulating film is formed on the wafer surface. In step 4 13 (electrode formation step), electrodes are formed on the wafer by vapor deposition. In step 4 14 (ion implantation step), ions are implanted into the wafer. Each of the above steps 411 to 4141 constitutes a pre-processing step in each stage of wafer processing, and is selected and executed according to a necessary process in each stage.

 In each stage of the wafer process, when the above-mentioned pre-processing step is completed, the post-processing step is executed as follows. In this post-processing step, first, in step 415 (register forming step), a photosensitive agent is applied to the wafer. Subsequently, in step 416 (exposure step), the circuit pattern of the mask is transferred onto the wafer by the lithographic system (exposure apparatus) and the exposure method described above. Next, in step 417 (development step), the exposed wafer is developed, and in step 418 (etching step), the exposed members other than the portion where the resist remains are removed by etching. Then, in step 419 (resist removing step), the unnecessary resist after etching is removed.

 By repeating these pre-processing and post-processing steps, multiple circuit patterns are formed on the wafer.

If the device manufacturing method of the present embodiment described above is used, the exposure apparatus and the exposure method of each of the above embodiments are used in the exposure step (step 4 16). Therefore, it is possible to improve the line width controllability by improving the exposure amount control accuracy, thereby improving the exposure accuracy including the overlay accuracy and improving the yield of highly integrated devices with good yield. Can be produced. Industrial applicability

 As described above, the exposure apparatus and the exposure method according to the present invention form a fine pattern on a substrate such as a wafer with high accuracy in a lithographic process of manufacturing a micro device such as an integrated circuit. Suitable for Further, the device manufacturing method according to the present invention is suitable for manufacturing a device having a fine pattern.

Claims

The scope of the claims

1. An exposure method performed by an exposure apparatus having an optical system for transferring a pattern illuminated by exposure light from a light source onto a substrate,

 A first step of setting an exposure amount control target value according to the transmittance of the optical system; and controlling the pattern via the optical system while controlling the exposure amount based on the set exposure amount control target value. A second step of transferring onto the substrate.

2. The exposure method according to claim 1,

 An exposure method, wherein a transmittance of the optical system, which is a reference for setting an exposure control target value in the first step, is actually measured at a predetermined measurement interval.

3. The exposure method according to claim 2,

 The exposure method according to claim 1, wherein the measurement interval is set according to exposure conditions.

4. The exposure method according to claim 3,

 The exposure method, wherein the exposure condition includes a transmittance of a mask.

5. The exposure method according to claim 3,

 The exposure control method according to claim 1, wherein the exposure condition includes one of a minimum line width and an exposure allowable error.

6. The exposure method according to claim 2, The exposure method according to claim 1, wherein the measurement interval is changed in accordance with an amount of change between the transmittance obtained by the immediately preceding transmittance measurement and the transmittance obtained by the previous transmittance measurement.

7. The exposure method according to claim 1,

 The first step is a prediction function determining step of determining a time change prediction function of the transmittance of the optical system according to an irradiation history of the exposure light to the optical system;

 Setting an exposure amount control target value based on the determined transmittance temporal change prediction function.

8. The exposure method according to claim 7,

 The time change function is defined as: T is an optical system transmittance, a is a parameter representing the change rate, and b i is a parameter dependent on each exposure condition including an illumination condition.

T = aexp

An exposure method, which is a function represented by:

9. The exposure method according to claim 7,

 Prior to the predictive function determining step, the method further includes a step of measuring a time during which the apparatus was previously stopped for operation, an irradiation time of exposure light to the optical system during self-cleaning, an exposure light intensity, and an integrated irradiation amount. Characteristic exposure method.

10. The exposure method according to claim 7,

 An exposure method, wherein environmental conditions of the optical system are measured at predetermined time intervals, and these factors are taken into account when determining the time change prediction function of the transmittance.

1 1. The exposure method according to any one of claims 7 to 0, An exposure method, further comprising the step of measuring the transmittance of the optical system at predetermined intervals, wherein the transmittance time change prediction function is corrected each time the transmittance is measured.

1 2 In the exposure method according to claim 11,

 The exposure method according to claim 1, wherein the transmittance measurement interval is determined according to a relationship with required exposure accuracy.

13 In the exposure method according to claim 11,

 The exposure method according to claim 1, wherein the measurement interval of the transmittance is short in a period in which the rate of change of the optical system transmittance is large, and is long in the opposite case.

14. An exposure apparatus for transferring a pattern illuminated by exposure light from a light source onto a substrate using an optical system,

 An exposure setting device that sets an exposure control target value in accordance with the transmittance of the optical system;

 An exposure control system that controls an exposure based on the set exposure control target value.

15. The exposure apparatus according to claim 14, wherein

 Further comprising a transmittance measurement device for measuring the transmittance of the optical system,

 The exposure apparatus, wherein the exposure setting apparatus sets the exposure control target value according to the transmittance measured by the transmittance measuring apparatus.

16 In the exposure apparatus according to claim 15,

The transmittance measurement device performs the transmittance measurement at a predetermined measurement interval. Exposure apparatus.

17. The exposure apparatus according to claim 16, wherein

 An exposure apparatus, further comprising a control device for setting a measurement interval of the transmittance measurement device according to exposure conditions.

18. The exposure apparatus according to claim 17,

 Further comprising an information reading device for reading information of the mask on which the pattern is formed,

 The exposure apparatus, wherein the control device automatically sets a measurement interval of the transmittance measurement device based on the read information of the mask.

1 9. The exposure apparatus according to claim 16,

 A control unit that sets a measurement interval of the transmittance in the transmittance measurement device according to a variation amount between the transmittance measured immediately before by the transmittance measurement device and the transmittance measured before the transmittance measurement device. Exposure equipment characterized.

20. The exposure apparatus according to claim 19,

 An exposure apparatus, wherein two consecutive measurements of the transmittance by the transmittance measurement apparatus are performed prior to the start of exposure.

21. The exposure apparatus according to claim 19,

 An exposure apparatus, wherein two consecutive measurements of the transmittance by the transmittance measurement apparatus are performed after the start of exposure.

22. The exposure apparatus according to claim 14, A first optical sensor for detecting a light amount of the exposure light applied to the pattern,

 An exposure apparatus, wherein the exposure control system controls an exposure based on an exposure control target value and an output of the first optical sensor during transfer of the pattern to the substrate.

23. The exposure apparatus according to claim 15,

 The transmittance measuring device includes: a first optical sensor that detects a light amount of the exposure light applied to the pattern; a second optical sensor provided on substantially the same surface as the substrate; and a second optical sensor. An optical sensor is used to detect the amount of the exposure light that has passed through the optical system at the time of exposure according to the exposure condition, and the transmittance of the optical system is determined based on the amount of light and the output of the first optical sensor. An exposure apparatus comprising: a control device to be sought.

24. The exposure apparatus according to claim 23,

 The exposure apparatus, wherein the exposure control system controls an exposure based on the target value of the exposure control and an output of the first optical sensor during the transfer of the pattern to the substrate.

25. The exposure apparatus according to claim 23,

 An exposure apparatus, wherein the control device performs light amount detection of the exposure light that has passed through the optical system at an evening according to a transmittance of a mask on which the pattern is formed.

26. The exposure apparatus according to claim 23,

The control device may be configured to adjust the timing based on either the minimum line width or the exposure tolerance. Detecting the light amount of the exposure light that has passed through the optical system by scanning.

 27. The exposure apparatus according to claim 14, wherein

 An arithmetic unit that determines a time change prediction function of the transmittance of the optical system according to an irradiation history of the exposure light to the optical system,

 The exposure apparatus, wherein the exposure setting apparatus sets the exposure control target value based on a transmittance time change prediction function determined by the arithmetic unit.

28. The exposure apparatus according to claim 27,

 A transmittance measuring device for measuring the transmittance of the optical system at predetermined intervals;

 An exposure apparatus, further comprising: a correction device that corrects the transmittance time change prediction function each time the transmittance is measured.

29. The exposure apparatus according to claim 28,

 A control unit that sets a measurement interval of the transmittance in the transmittance measurement device according to a variation amount between the transmittance measured immediately before by the transmittance measurement device and the transmittance measured before the transmittance measurement device. Exposure equipment characterized.

30. The exposure apparatus according to claim 14, wherein

 The optical system includes an illumination optical system that illuminates the mask on which the pattern is formed with the exposure light, and a projection optical system that projects the exposure light emitted from the mask onto the substrate,

An exposure apparatus, further comprising: a mask stage for holding the mask on which the pattern is formed; and a substrate stage for holding the substrate.

31. The exposure apparatus according to claim 30, wherein

 An exposure apparatus further comprising: a driving device that synchronously moves the mask stage and the substrate stage in a one-dimensional direction in a plane orthogonal to an optical axis of the projection optical system.

32. A method for manufacturing an exposure apparatus for transferring a pattern of a mask onto a substrate, the method comprising: providing an illumination optical system for irradiating the mask with exposure light;

 Providing a projection optical system for projecting the exposure light emitted from the mask onto the substrate;

 Providing a substrate stage for holding the substrate;

 Providing an exposure setting device that sets an exposure control target value in accordance with the transmittance of the projection optical system;

 Providing an exposure control system that controls the exposure based on the set exposure control target value.

33. The method of manufacturing an exposure apparatus according to claim 32,

 Providing a mask stage for holding the mask;

 Providing a driving device for synchronously moving the mask stage and the substrate stage in a one-dimensional direction within a plane perpendicular to the optical axis of the projection optical system. .

3 4. In a device manufacturing method including a lithographic process,

 A device manufacturing method, wherein in the lithographic process, exposure is performed using the exposure method according to any one of claims 1 to 10.

35. Manufactured using the exposure apparatus according to any one of claims 14 to 31. Device _c